1. Field of the Invention
The invention relates to a cable with at least two wire pairs which are in each case configured for the transmission of a differential data signal. In particular, the invention relates to a USB cable, for example a USB 3.0 cable or a USB 3.1 cable.
2. Description of Related Art
The transmission of USB signals is necessary for an extremely wide range of technical applications. For example, a USB socket may be desired in a rear part of a vehicle in order to allow USB devices to be plugged in, which means that a USB cable needs to be led through the vehicle from the front to the rear. USB sockets or USB connections can also be required in different locations (offices, public institutions, means of transport etc.) for the connection of USB devices, whereby USB cables need to be laid for this purpose.
Conventional USB2 interfaces (for example USB 2.0 interfaces) only have one signal wire pair (D+ and D−) and a wire pair for power supply (GND, VBUS). The data transmission takes place symmetrically via the signal wire pair, the data signal (“signal part”) being transmitted through one wire of the signal wire pair and the corresponding inverted data signal (“reference part”) being transmitted through the other wire. For this purpose, a cable for the transmission of USB2 signals uses two twisted and shielded wires as the signal conductor pair in order to minimize interference with transmission. The receiver of the signal determines the differential voltage of the data signal transmitted differentially via the signal wire pair, so that interference signals acting to an equal extent on both wires of the signal wire pair are eliminated.
A few years ago, the USB3 standard was introduced. USB3 interfaces (for example USB3.0 interfaces) have, in addition to the connections explained above (D+, D−, GND, VBUS) at least two additional signal wire pairs (SSTX+ and SSTX−; SSRX+ and SSRX−). A differential data signal is transmitted via each of these two signal wire pairs. Overall, this allows higher data rates to be achieved than with the conventional USB2 standard.
A conventional USB 3.0 cable is illustrated in FIG. 2. It shows three twisted wire pairs (twisted pairs 112, 114, 116), each configured for transmission of a differential data signal. A ground conductor in the form of a drain wire 115 can in each case be provided adjacent to the twisted wire pairs. In addition, two (untwisted) wires 122, 124 are provided for the power supply. The individual wire pairs are in each case surrounded by a foil shield, and all the wires are surrounded by a common shield 130 and a protective sheath 150. In addition, filler elements 140 can be provided in order to ensure that the cable is round in cross section.
It has been found that, in such a conventional wire arrangement, depending on the path of and distance between the wire pairs in the cable, a crosstalk of varying intensity can occur between the individual wire pairs. Moreover, a conventional USB 3.0 cable is comparatively thick, which makes simple and space-saving installation difficult.
Known from WO 2013/033950 A1 and U.S. Pat. No. 6,452,107 B1 are cables with at least two wire pairs for the transmission of a differential data signal, wherein the at least two wire pairs extend in the longitudinal direction of the cable in a helical arrangement around a common stranding center.